The biological and chemical processes occurring in our bodies depend on a consistent environment.

Homeostasis is our bodys system for maintaining that consistency.

4Homeostasis Acid-Base

Metabolic processes within our bodies function within a very narrow pH range.

Many diseases and environmental influences can greatly impact this delicate range.

5Lets First Review

SpO2 90-100 (measures saturated hemoglobin through skin)

SaO2 90-100 (measures saturated hemoglobin in arterial blood)

6More review

PaCO2 35-45 (dissolved CO2 in blood)

PaO2 80-100 for adult and child

40-70 for newborn

60-80 for geriatric (measures dissolved oxygen in blood)

7Matilda

Matilda is 87 years old. Her doctor has called and told her to come down because her blood gasses were off in her labs. These are her labs.

SpO2 68

PaCO2 50

PaO2 55

8Who cares?

You do! Because the more we know about acid-base derangements the better we can treat patients in order to correct the derangements.

9Acids and Bases

Here we go!

10Acids

A substance that releases H Ions when dissolved in water

Lactic acid

Ketones

Carbonic acid

11Bases

Also known as alkalis, these are H seekers and also dissociate in water. When bases dissolve in water the hydroxyl ion is released (OH-) this little guy actively seeks out and attaches itself to acids floating around in the blood-stream.

Bicarbonate is most common base.

OH- CO2 HCO3

12Acid-Base Physiology

During energy production, byproducts are released. Two of these main byproducts effect acid-base.

Carbon dioxide (CO2)

Hydrogen (H)

13Control that Hydrogen

The key to acid-base regulation is controlling hydrogen ion concentrations.

14pH

P-what? I thought we were talking about hydrogen.

The hydrogen ion concentration outside the cell is typically 4x10-8 mols/L or 0.00000004 equivalents per liter.

That number is to small to work with so we use the pH scale instead.

15pH Scale

Potential of Hydrogen

1-14

7 is mid-range

7.35-7.45 is normal for human body.

Hmm? So are we acidic or alkaloid?

16pH and Hydrogen

pH levels are inversely proportional to H

This means as H increases pH decreases and as pH increases, H decreases.

17(No Transcript) 18Hmm So?

If we are normally 7.35 to 7.45 and that is considered slightly alkaloid then at what point are we acidotic?

Anything below 7.35 is acidotic to humans and anything above 7.45 is alkaloid.

0.4 either way is as far as we like to go. About 6.9 acid and 7.8 alkalin.

19Fatal Values

pH of less than 6.9 and pH of greater than 7.8 are typically not conducive with life.

20Picky Picky

The body must maintain a fairly narrow alkaline environment in order for things to go smoothly.

Any imbalances can be very serious.

21Back to Matilda

So here are her values from before and now what do you think that means to her pH?

SaO2 68

PaCO2 50

PaO2 55

pH 7.23

22How do we keep it all balanced? 23Balancing Systems

Buffer System

Respiratory System

Renal System

24Buffer System

Fastest acting (nano-seconds)

Considered the chemical sponge (too much H use a sponge to clean it up. Or, need more give it a squeeze)

It can collect hydrogen ions when they are over-abundant and release them when they are scarce.

25How does it work?

Basically the cells produce CO2 and H during metabolism. The buffer system will change those two through chemical reactions to keep things balanced.

H lt-gt HCO3 lt-gt - H2CO3 lt-gt - H2O lt-gt CO2

Hydrogen Bicarb Carbonic Acid Water Carbon Dioxide

26Gosh! Whats that mean?

Easyif the body needs more acid, the buffer system takes water and carbon dioxide and makes carbonic acid (with the help of the enzyme carbonic anhydrase). Then carbonic acid can be split apart to make bicarbonate and hydrogen. This can go both directions

27Respiratory System

Second fastest to respond (usually within minutes)

Triggered by Chemoreceptors in the vessels.

Example Diabetic keto-acidosis

28Breathe!

When the pH gets a little out-o-wack a message is sent to the lungs. It tells them whether to breathe faster and harder or slower and more shallow.

29How does that work?

Hydrogen binds with bicarbonate. This makes carbonic acid. Carbonic acid then breaks down into water and carbon dioxide.

In red blood cells carbon dioxide is carried to the lungs and exchanged for oxygen.

The majority of CO2 is transported as bicarbonates in the plasma

30So in the lungs?

Oxygen has an affinity to hemoglobin and it climbs on board kicking off the CO2

The CO2 and water are displaced and through osmosis and diffusion are blown out with expiration of air.

31Gee Whiz!

After the CO2 has been blown away in the lungswhat happens?

Exactly! The pH increases, bringing the body back to normal.

32Renal System

If the lungs and buffers are not able to keep up with the amount of acids, then the kidneys must take action.

It may take the kidneys hours or days to react to an imbalance.

33What do the kidneys do to help?

They regulate pH by expelling excess hydrogen or bicarbonate ions.

The kidney tubules are smart. When they expel one ion they will exchange it for another.

34Kidneys work OT with COPD

When someone chronically retains CO2 the kidneys become the primary balancing system.

Example is the chronic emphysema patient. They rely entirely on the renal system to maintain pH.

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